Method for fixing optical member and optical unit

ABSTRACT

A method for fixing an optical member of an optical unit including the optical member and a holding member is provided. The holding member includes positioning portions for positioning the optical member. The optical member and the holding member are fixed to each other upon laser welding of a plurality of locations of the holding member other than the positioning portions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical unit in which an opticalmember such as a pickup lens and a holding member are fixed to eachother by laser welding by using laser light and to a method for fixingthe optical member.

2. Description of the Related Art

The following methods for fixing an optical member such as a lens arehitherto known.

(1) After inserting a lens in a lens-holding member composed of a resin,the lens is fixed to the peripheral front edge of the lens-holdingmember by known thermal caulking or the like; and

(2) The external periphery of a lens and a lens-holding member are fixedto each other with a UV cure adhesive or the like.

Unfortunately, according to the method (1), a caulking tool melts theperipheral front edge of the lens-holding member by heat so as to coverthe peripheral front edge of the lens, thereby leading to a longer timefor caulking and an increase in assembling steps, accordingly resultingin an increased cost. Also, since the external periphery of thelens-holding member must be melted by heat with the caulking tool so asto have the peripheral front edge of the lens fixed thereto, thelens-holding member and the lens are inevitable subjected to a pressingforce, thereby causing a guarantee problem of the positioning accuracyof the lens after assembly.

Also, according to the method (2), in a time period after application ofa UV cure adhesive to irradiation of a ultra-violet ray, the liquidadhesive is flown out onto the peripheral surface of the lens-holdingmember, and when the flown-out adhesive is solidified with ultra-violetradiation, the solidified adhesive interferes with components around thesolidified adhesive after assembly, thereby causing poor operation,especially deteriorating optical performance. Also, the liquid adhesiveflows inside the lens through a gap between the lens-holding member andthe external periphery of the lens, thereby causing a guarantee problemof the optical performance of the lens, or the like.

In order to solve these problems, Japanese Patent Laid-Open No.2003-123512 discloses a method in which two resins are fixed to eachother by laser welding. More particularly, a lens unit is made up by anouter lens composed of a transparent thermoplastic resin and a housingcomposed of a thermoplastic resin absorbent to laser light, and thehousing and the outer lens are welded with each other by emitting laserlight from a side wall of the outer lens in a state in which theexternal periphery of the housing and the side wall are abutted againsteach other.

Also, methods for fixing an optical member such as a plastic lens to alens frame or the like composed of a plastic by using laser light aredisclosed. For example, Japanese Patent Laid-Open No. 2004-20867discloses a method for fixing a plastic lens to, for example, a plasticlens-frame or a plastic finder frame by irradiating the lens-frame orthe finder-frame with laser light.

In addition, Japanese Patent Laid-Open No. 2003-123506 discloses amethod in which an outer lens composed of a transparent thermoplasticresin and a housing composed of another thermoplastic resin absorbent tolaser light are welded with each other by irradiating the entireperiphery of an inner sheet composed of a transparent thermoplasticresin with laser light from the outer lens side in a state in which theinner sheet is sandwiched at the abutment portion between the outer lensand the housing.

SUMMARY OF THE INVENTION

The present invention is directed to a method for fixing an opticalmember to a holding member. In one aspect of the present invention, amethod for fixing an optical member to a holding member includes thesteps of inserting the optical member in the holding member; andirradiating the holding member with a plurality of beams of laser lightsubstantially at the same time, passing through the optical member.

The present invention is also directed to a holding member for holdingan optical member. In another aspect of the present invention, a holdingmember, holding an optical member and fixed by a laser irradiationprocess, includes a plurality of positioning portions adapted to contactwith the optical member so as to position the optical member prior tothe laser irradiation process; and a plurality of laser irradiationportions protruding lower than the positioning portions and beingirradiated with the laser light in the laser irradiation process.

The present invention is further directed to an optical unit. In yetanother aspect, an optical unit includes an optical member; a holdingmember holding the optical member and having a wall formed therein so asto face an external periphery of the optical member; and an intermediatemember disposed between the external periphery of the optical member andthe wall of the holding member, the intermediate member including athermoplastic resin absorbent to laser light such that at least a partof the intermediate member is melted upon irradiation with laser lightso as to fix the optical member to the holding member.

Further features and advantages of the present invention will becomeapparent from the following description of exemplary embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective sectional view of a lens unit, illustrating amethod for fixing a lens, according to a first embodiment of the presentinvention.

FIG. 2 is a sectional view of the lens unit, illustrating the method forfixing a lens, according to the first embodiment.

FIG. 3 is a perspective sectional view of a lens unit, illustrating amethod for fixing a lens, according to a second embodiment of thepresent invention.

FIG. 4 is a sectional view of the lens unit, illustrating the method forfixing a lens, according to the second embodiment.

FIG. 5 is a perspective sectional view of a lens unit, illustrating amethod for fixing a lens, according to a third embodiment of the presentinvention.

FIG. 6 is a sectional view of the lens unit, illustrating the method forfixing a lens, according to the third embodiment.

FIG. 7 is a perspective sectional view of a lens unit, illustrating amethod for fixing a lens, according to a fourth embodiment of thepresent invention.

FIG. 8 is a sectional view of the lens unit, illustrating the method forfixing a lens, according to the fourth embodiment.

FIG. 9 is a perspective sectional view of a lens unit, illustrating amethod for fixing a lens, according to a fifth embodiment of the presentinvention.

FIG. 10 is a sectional view of the lens unit, illustrating the methodfor fixing a lens, according to the fifth embodiment.

FIG. 11 is a perspective sectional view of the lens unit fixed to a lensframe, according to the lens fixing method of the first embodiment,viewed from an opposite direction to a laser irradiation direction.

FIG. 12 is a perspective sectional view of the lens unit fixed to thelens frame, according to the lens fixing method of the secondembodiment, viewed from an opposite direction to a laser irradiationdirection.

FIG. 13 is a perspective sectional view of the lens unit fixed to thelens frame according to the lens fixing method of each of the third andfourth embodiments, viewed from an opposite direction to a laserirradiation direction.

FIG. 14 is a perspective sectional view of the lens unit fixed to a lensframe, according to the lens fixing method of the first embodiment,viewed from an opposite direction to a laser irradiation direction.

FIG. 15 is a perspective sectional view of a major part of an opticalunit according to a sixth embodiment of the present invention.

FIG. 16 is a perspective sectional view of a major part of the opticalunit according to the sixth embodiment, having a lens inserted therein.

FIG. 17 is a perspective sectional view of a major part of an opticalunit according to a seventh embodiment of the present invention.

FIG. 18 is a perspective sectional view of a major part of the opticalunit according to the seventh embodiment, having a lens insertedtherein.

FIG. 19 is a perspective sectional view of a major part of an opticalunit according to an eighth embodiment of the present invention.

FIG. 20 is a sectional view of the optical unit according to the eighthembodiment, illustrating its state in which a lens-holding member has alens and a ring-shaped member inserted therein.

FIG. 21 is a perspective sectional view of a major part of an opticalunit according to a ninth embodiment of the present invention.

FIG. 22 is a sectional view of the optical unit according to the ninthembodiment, illustrating its state in which a lens-holding member has alens and a ring-shaped member inserted therein.

DESCRIPTION OF THE EMBODIMENTS First Embodiment

FIG. 1 is a perspective sectional view of a lens unit, illustrating amethod for fixing a lens according to a first embodiment.

The lens-fixing method according to the first embodiment will bedescribed. A first lens 11 is fitted into a lens frame 13 such that apositioning portion 11 a of the first lens 11 is abutted against afirst-lens positioning portion 13 h of the lens frame 13. Then, a secondlens 12 is fitted into the lens frame 13 such that a positioning portion12 a of the second lens 12 is abutted against a second-lens positioningportion 13 a of the lens frame 13. In this state, the optical axes ofthe first and second lenses 11 and 12 are aligned with a virtual axisZ1. Since the external peripheral dimension of each of walls 13 i and 13e of the lens frame 13 is slightly greater than that each of the firstand second lens 11 and 12, the position of each of the first and secondlenses 11 and 12 can be adjusted in a direction orthogonal to the axisZ1 by making use of the above clearance. Accordingly, the optical axisof each lens can be aligned with the axis Z1 by certain methods (notshown). Then, a plurality of locations of each lens is spot-irradiatedwith laser light at the same time from above the lens. Regarding laserirradiation, the second lens 12 may be irradiated with laser light 14 aafter irradiation of the first lens 11 with laser light 14 b, or bothlenses may be irradiated with the laser light 14 a and 14 b at the sametime. Alternative, after fixing either one of the lenses with anadhesive or the like, the other lens may be irradiated with laser light.Further, in order to increase a fixing strength, laser irradiation maybe performed a plurality of times while changing laser irradiationlocations of each lens.

Since most part of laser light passes through the lenses, most part ofits energy reaches the lens frame 13. The lens frame 13 is composed of aplastic absorbing energy in a range of wavelengths of laser light.

FIG. 2 is a sectional view of the lens unit, illustrating the method forfixing a lens by laser irradiation, according to the first embodiment.

An example fixing method of simultaneously irradiating the two beams oflaser light 14 a and 14 b will be described. The beams 14 a and 14 b oflaser light are absorbed at the respective lens-positioning portions 13a and 13 h of the lens frame 13, are changed into heat, and cause themargin of each laser irradiation portion to be melted. The melted partof plastic constituting the lens frame 13 enters fine irregularities ofthe lens surfaces of abutment portions (that is, the positioningportions) 11 a and 12 a of the first lens 11 at which the plastic isabutted against the first and second lenses 11 and 12, respectively.

When the laser irradiation is stopped, although the melted part ofplastic is quickly cooled and contracts, at least a part of the plasticentering the fine irregularities of the lens surfaces remains in theirregularities, thereby resulting in fixing the lenses and the lensframe to each. The above-mentioned lens-fixing portions are formed at aplurality of locations of the lens-positioning portions 13 a and 13 h atthe same time, whereby the first and second lenses 11 and 12 are fixedto the lens frame 13 without inclination relative to the axis Z1.

FIG. 11 is a perspective sectional view of a lens assembly assembled bythe lens fixing method according to the first embodiment, viewed from anopposite direction to a laser irradiation direction.

Second Embodiment

FIG. 3 is a perspective sectional view of a lens unit, illustrating amethod for fixing a lens, according to a second embodiment.

The lens-fixing method according to the second embodiment will bedescribed. As shown in FIG. 3, after being abutted against a lens-fixingportion 23 f of a lens frame 23 from below the lens frame 23, a firstlens 21 is fixed to the lens frame 23 by deforming a portion 23 g of thelens frame 23 by thermal caulking or the like.

Then, a second lens 22 is fitted into the lens frame 23 such that apositioning portion 22 a of the second lens 22 is abutted against asecond-lens positioning portion 23 a of the lens frame 23. The lensframe 23 has a plurality of laser-irradiation portions 23 b disposedtherein. Although the laser-irradiation portions 23 b are formed so asto face an external peripheral corner 22 b of the second lens 22, thelaser-irradiation portions 23 b and the external peripheral corner 22 bof the second lens 22 do not contact each other. In this state, theoptical axes of the first and second lenses 21 and 22 are aligned withthe virtual axis Z1. Since the external peripheral dimension of a wall23 e of the lens frame 23 is slightly greater than that of the secondlens 22, by making use of this clearance, the optical axis of the secondlens 22 can be aligned with the axis Z1 with the method (not shown) asin the first embodiment. Then, a plurality of locations of each lens isspot-irradiated with laser light at the same time from above the lens.The irradiation direction of the laser light may be parallel to theoptical axis of the lens or orthogonal to the laser-irradiation portions23 b. Alternatively, after irradiation with a plurality of beams oflaser light 24 a, another plurality of laser irradiation portions may beirradiated with laser light 24 c.

FIG. 4 is a sectional view of the lens unit, illustrating the method forfixing a lens by laser irradiation, according to the second embodiment.

The laser light 24 a passes through the lens, is absorbed at thelaser-irradiation portion 23 a of the lens frame 23, is changed intoheat, and causes the margin of each laser irradiation portion to bemelted. The melted part of plastic constituting the lens frame expandsthermally, comes into contact with the external peripheral corner 22 bof the second lens 22, and resultantly enters fine irregularities of thelens surfaces.

When the laser irradiation is stopped, although the melted part ofplastic is quickly cooled and contracts, at least a part of the plasticentering the fine irregularities of the lens surfaces remains in theirregularities, whereby the lenses and the lens frame are fixed to eachother. Since the laser-irradiation portions 23 b are formed at locationsof the lens frame 23 other than the lens-positioning portion 23 a, andthe lens-positioning portion 23 a is not irradiated with laser light,the lens-positioning portion 23 a is not thermally deformed. Also, aplurality of the laser-irradiation portions 23 b is irradiated with thelaser light 24 a substantially at the same time, whereby the second lens22 is fixed to the lens frame 23 without inclination relative to theaxis Z1.

FIG. 12 is a perspective sectional view of a lens assembly assembled bythe lens fixing method according to the second embodiment, viewed froman opposite direction to a laser irradiation direction.

Third Embodiment

FIG. 5 is a perspective sectional view of a lens unit for fixing a lensaccording to a third embodiment, and FIG. 6 is a sectional view of thelens unit, illustrating the method for fixing a lens by laserirradiation, according to the third embodiment. Only parts differentfrom those in the second embodiments will be described.

A second lens 32 is fitted into a lens frame 33 such that a positioningportion 32 a of the second lens 32 is abutted against positioningportions 33 a of a lens frame 33. The lens frame 33 has pluralities ofthe lens-positioning portions 33 a and laser-irradiation portions 33 balternately disposed therein. The laser-irradiation portions 33 b lielower than the lens-positioning portions 33 a. In a state in which thesecond lens 32 is fitted in the lens frame 33, the laser-irradiationportions 33 b and the second lens 32 have a gap s formed therebetween.In the same fashion as in the first embodiment, the optical axes offirst and second lenses 31 and 32 are aligned with the virtual axis Z1in this state. Then, laser light 34 a is emitted towards thelaser-irradiation portions 33 b. Upon being absorbed at thelaser-irradiation portions 33 b of the lens frame 33, the laser light 34a is changed into heat and causes the margin of each laser irradiationportion to be melted. The melted part of plastic constituting the lensframe 33 expands thermally and comes into contact with the positioningportion 32 a of the second lens 32, thereby resulting in the meltedportion entering irregularities of the lens surfaces. The gap s can liein a region smaller than about 0.1 mm. When the gap s greater than 0.1mm, a larger amount of energy is needed for thermally expanding the lensframe so as to cause the lens and lens frame to come into contact witheach other; hence requiring a larger volume of the melted part ofplastic, leading to greater thermal influence on components around themelted part.

When the laser irradiation of the laser light 34 a is stopped, althoughthe melted part of plastic is quickly cooled and contracts, at least apart of the plastic entering the abutment with the lens remains in theabutment, thereby resulting in fixing the lens and the lens frame toeach other. Since the laser-irradiation portions 33 b and thelens-positioning portions 33 a are formed at mutually differentlocations of the lens frame 33, and the laser light 34 a is not emittedtowards the lens-positioning portions 33 a, the lens-positioningportions 33 a are not thermally deformed. The lens frame 33 has athickness-reduced portion 33 d formed at the back of thelaser-irradiation portions 33 b so as to be thinner than other partsthereof around the laser-irradiation portions 33 b. With thethickness-reduced portion 33 d, a contracting action of the melted partof plastic advances quickly, and also, the lens frame 33 holds anelastic force obtained due to reduction in thickness, even after thelens is fixed to the lens frame. Since a plurality of thelaser-irradiation portions 33 b are irradiated with the laser light 34 asubstantially at the same time, the second lens 32 is fixed withoutinclination relative to the axis Z1. In addition, due to the elasticforce, the lens frame has a force pressing the lens against thelens-positioning portions 33 a and also another force restoring the lensagainst an external force such as shock.

FIG. 13 is a perspective sectional view of a lens assembly assembled bythe lens fixing method according to the third embodiment, viewed from anopposite direction to a laser irradiation direction.

Fourth Embodiment

FIG. 7 is a perspective sectional view of a lens unit, illustrating amethod for fixing a lens according to a fourth embodiment, and FIG. 8 isa sectional view of the lens unit, illustrating the method for fixing alens by laser irradiation, according to the fourth embodiment. Onlyparts different from those in the third embodiment will be described.

A lens frame 43 has pluralities of lens-positioning portions 43 a andlaser irradiation surfaces 43 b alternately disposed therein. Each ofthe laser irradiation surfaces 43 b has a spherical projection 43 cformed thereon. The laser irradiation surfaces 43 b lie lower than thelens-positioning portions 43 a. In a state in which a second lens 42 isfitted in the lens frame 43 such that the surface of the second lens 42is abutted against the lens-positioning portions 43 a, the projection 43c additionally formed on the corresponding laser irradiation surface 43b does not come into contact with the second lens 42. Further, even whenthe second lens 42 is somewhat moved for adjusting its optical axis, theoptical axis can be aligned without affecting its positioning accuracy.

While the laser irradiation surfaces are flush with one another in thethird embodiment, in the fourth embodiment, only the projections 43 cformed on the respective laser irradiation surfaces 43 b are irradiatedwith laser light. With this arrangement, a lesser amount of heat istransferred to the lens-positioning portions 43 a.

The projection 43 c on the corresponding laser irradiation surface 43 bis not limited to having a spherical shape and may have a shape such asa cylindrical or prismatic shape.

Fifth Embodiment

FIG. 9 is a perspective sectional view of a lens unit, illustrating amethod for fixing a lens according to a fifth embodiment of the presentinvention, and FIG. 10 is a sectional view of the lens unit,illustrating the method for fixing a lens by laser irradiation,according to the first embodiment. Only parts different from those inthe fourth embodiment will be described.

A lens frame 53 has pluralities of lens-positioning portions 53 a andlaser irradiation portions 53 b alternately disposed therein, and thelaser irradiation portions 53 b have cuts formed at the margin thereofand cut away from a wall 53 e of the lens frame 53. In addition, thelaser irradiation surfaces 53 b have projections 53 c formed thereon. Asecond lens 52 includes a positioning surface 52 a for being positionedwith respect to the lens frame and a slope 52 b facing thelaser-irradiation portions 53 b. Although the lenses are fixed to thelens frame by irradiating the projections 53 c formed on the laserirradiation surfaces 53 b with laser light 54 in the same fashion as inabove-described embodiments, since the laser-irradiation portions 53 bhave the cuts at the margin thereof, a thermal contraction force afterirradiation of the laser light is more likely exerted on the second lens52 towards the lens-positioning portions 53 a than in the otherembodiments, and also, an elastic force is likely exerted on thelaser-irradiation portions 53 b, thereby more effectively preventing thelenses from disengagement from the lens frame due to shock or the likethan in the other embodiments.

While a plurality of locations is irradiated with laser light at thesame time in each of the above-described embodiments, the locations arenot irradiated at the same time in a narrow sense and may be irradiatedwith the laser light in a time range of, for example, several tens toseveral hundred milliseconds as long as the time range does notadversely affect positional accuracy of the lenses.

When a lens to be fixed is composed of glass in each embodiment, inorder to increase the welding strength of the lens with the melted partof plastic, the surface of a welding portion of the lens may beprocessed so as to be rougher than the curved surface of the lens or maybe subjected to a primer process.

Also, a lens to be fixed may be composed of plastic in each embodiment.

In the case of a plastic lens, the lens and the lens frame may be weldedwith each other such that heat of the lens frame melted due to laserirradiation causes a part of the plastic lens to be melted and to bethus chemically bonded to the plastic constituting the lens frame.

A member to be fixed is not limited to a lens and may be an opticalelement such as a transparent glass, a plastic plate or an opticalfilter.

Sixth Embodiment

FIGS. 15 and 16 illustrate an optical unit inserted in a camera,according to a sixth embodiment of the present invention. Moreparticularly, FIG. 15 is a perspective sectional view of a major part ofthe optical unit, and FIG. 16 is a sectional view of a major part of theoptical unit, illustrating a state in which the optical unit iscompletely inserted.

As shown in these figures, the lens unit includes a lens 101 whichserves as one of optical members forming an image of pickup light from asubject onto a pickup element (not shown) and which has a depression 101a having a substantially V-shaped cross-portion formed on the externalperipheral surface thereof; a lens-holding member 102 holding the lens101 and having a lens-receiving portion 102 a; and a ring-shaped member103 lying between the depression 101 a of the lens 101 and thelens-receiving portion 102 a of the lens-holding member 102 when theoptical unit is completely inserted as shown in FIG. 16. The ring-shapedmember 103 has a thermal plastic property and also a property absorbingnear infrared light and, in addition, is composed of a material havingan appropriate elasticity so as to climb over an external periphery 101b of the lens 101 and to be fitted into the depression 101 a prior tothe insertion of the lens unit.

A laser-irradiation apparatus 104 shown in FIG. 16 irradiates thering-shaped member 103 interposed between the depression 101 a of thelens 101 and the lens-receiving portion 102 a of the lens-holding member102 as described above, with laser light (near infrared light) 105, aswill be described later, so that the ring-shaped member 103 is meltedand the lens 101 is hence fixed to the lens-holding member 102.

A procedure for fixing the lens 101 and the lens-holding member 102 toeach other by laser welding will be described.

As shown in FIG. 16, the lens 101 holding the ring-shaped member 103 inthe depression 101 a having a substantially V-shaped cross-portion isfirst inserted into the lens-holding member 102. Then, thelaser-irradiation apparatus 104 irradiates a plurality of locations ofthe edge of the lens 101 with the spot-shaped laser light 105. With thisarrangement, the laser light 105 passes through the lens 101, and theplurality of locations of the ring-shaped member 103 is irradiated withthe laser light 105 substantially at the same time. Since thering-shaped member 103 is composed of a material absorbent to nearinfrared light as described above, upon being irradiated with the laserlight 105 as described above, the ring-shaped member 103 generates heatby absorbing the laser light 105, thermally expands, is melted, iswelded with the lens-receiving portion 102 a of the lens-holding member102, is filled in the depression 101 a of the external periphery of thelens 101, and is resultantly closely fixed to the lens 101.

When the laser irradiation is finished, and the irradiation portions arecooled, the ring-shaped member 103 and the lens-receiving portion 102 aof the lens-holding member 102 are brought into an integrated state bywelding, the ring-shaped member 103 is closely fixed to the depression101 a of the lens 101 in a form of being filled in the depression 101 a.As a result, the lens 101 is fixed to the lens-holding member 102 bywelding, having the depression 101 a interposed therebetween.Accordingly, even when a force is exerted on the lens 101 in a directionof detaching from the lens-holding member 102, the welding portion isformed in a shape of a so-called undercut, thereby providing anexcellent fixing feature of preventing the lens 101 from detaching fromthe lens-holding member 102 against a detaching force.

According to the foregoing sixth embodiment, the lens 101 has thedepression 101 a disposed at the external periphery thereof; thering-shaped member 103 fitted into the depression 101 a upon insertionof the lens 101 into the lens-holding member 102 and serving as anengagement is composed of a material different from that of thelens-holding member 102; and a plurality of locations of the ring-shapedmember 103 is irradiated with the laser light 105, whereby the lens 101and the lens-holding member 102 are fixed to each other by laserwelding. Since the lens 101 and the lens-holding member 102 are fixed toeach other by laser welding, having the depression 101 a interposedtherebetween, these components are fixed at a so-called undercut afterthe laser welding, whereby the lens unit has excellent fixing featuresof preventing the lens 101 from detaching from the lens-holding member102 against a detaching force and hence firmly fixing the lens 101 tothe lens-holding member 102.

While the depression 101 a is formed at the external periphery of thelens 101 in the above-described sixth embodiment, the present inventionis no limited to this arrangement. Even when a depression into which thering-shaped member 103 is fitted is formed at the internal periphery ofthe lens-holding member 102, the same advantages can be obtained. Also,although a plurality of the locations of the ring-shaped member 103 isirradiated with laser light, irradiation locations are not limited tothe above arrangement, and the ring-shaped member 103 may be irradiatedwith laser light around the entire circumference thereof.

One skilled in the art will appreciate that the lens 101 may be composedof even a glass or resin material. In the case where the lens 101 iscomposed of a resin material, upon irradiation with laser light, themelted ring-shaped member 103 causes a part of the resin lens to bemelted, whereby the lens 101 and the lens-holding member 102 arelaser-welded with each other, having the ring-shaped member 103interposed therebetween. As described above, the laser welding iscarried out through the depression 101 a of the lens 101, therebyproviding an excellent fixing feature of preventing the lens fromdetaching from the lens-holding member against a detaching force in thesame fashion as described above.

Although no description has been made about the surface of thedepression 101 a of the lens 101 in the above-described sixthembodiment, the lens may be formed so as to have a rough surface. Withthis structure, when the lens 101 is composed of a glass material by wayof example, the foregoing intermediate member fills in irregularities ofthe rough surface, whereby the lens 101 is more closely fixed to thelens-holding member 102.

Further, while the lens 101 is subjected to laser welding in a state ofbeing simply inserted in the lens-holding member 102 in theabove-described sixth embodiment, those skilled in the art willappreciate that the lens unit may have a structure in which eccentricityand inclination of the lens 101 are adjusted in a state of holding thelens 101, for example, by a vacuum-sucking tool, and, after theadjustment, the lens 101 is subjected to laser welding while the holdingstate is maintained. On this occasion, since the laser irradiationcauses the ring-shaped member 103 to expand thermally, thelens-receiving portion 102 a of the lens-holding member 102 and thedepression 101 a at the external periphery of the lens 101 are subjectedto laser welding, thereby providing an excellent fixing feature ofpreventing the lens from detaching from the lens-holding member againsta detaching force in the same fashion as described above.

Seventh Embodiment

FIGS. 17 and 18 illustrate an optical unit inserted in a camera,according to a seventh embodiment of the present invention. Moreparticularly, FIG. 17 is a perspective sectional view of a major part ofthe optical unit, and FIG. 18 is a sectional view of a major part of theoptical unit in a state of being completely assembled.

As shown in these figures, the optical unit includes a lens 111 servingas one of optical members forming an image of pickup light from asubject onto a pickup element (not shown); and a lens-holding member112. The lens 111 has a depression 111 a formed on the externalperipheral surface thereof, having a substantially V-shapedcross-portion. The lens-holding member 112 for holding the lens 111 iscomposed of a material absorbent to laser light (near infrared light)114, which will be described later, having a thermoplastic property, andhas a plurality of lens-receiving portions 112 a protruding in theoptical axis direction and formed at a substantially equal interval inthe circumferential direction, in addition to having projections 112 bprotruding in the radial direction, each formed at the top of therespective lens-receiving portion 112 a so as to be fitted into theexternal peripheral depression 111 a of the lens 111 as shown in FIG.18. Further, the projection 112 b is formed so as to be elasticallydeformable so that the projection can climb over an external periphery111 b (see FIG. 17) for insertion into the lens-holding member by aso-called light press-fitting force.

A laser-irradiation apparatus 113 shown in FIG. 18 emits near infraredlight 114 as will be described later.

A procedure of fixing the lens 111 and the lens-holding member 112 toeach other by laser welding will be described.

As shown in FIG. 18, the lens 111 is first inserted into thelens-holding member 112. Then, the laser-irradiation apparatus 113irradiates a plurality of locations of the edge of the lens 111 with thespot-shaped laser light 114. With this arrangement, the laser light 114passes through the lens 111 and causes the plurality of the projections112 b of the lens-holding member 112 to be irradiated therewithsubstantially at the same time. Since the projections 112 b of thelens-holding member 112 irradiated with the laser light 114 as describedabove are composed of a material absorbent to near infrared light asdescribed above, the projections 112 b generate heat by absorbing thelaser light 114, expand thermally, are melted, and fill in and areclosely fixed to the depression 111 a of the lens 111.

When the laser irradiation is finished, and the irradiation portions arecooled, the melted projections 112 b of the lens-holding member 112 aresolidified in a state of being closely fixed to the depression 111 a ofthe lens 111. As a result, since the lens 111 is fixed to thelens-holding member 112 by welding, having the depression 111 ainterposed therebetween, even when a force is exerted on the lens 111 ina direction of detachment from the lens-holding member 112, with thewelding portion formed in a shape of a so-called undercut, an excellentfixing feature of preventing the lens from detaching from thelens-holding member against a detaching force is provided.

According to the seventh embodiment, the lens 111 has the depression 111a disposed at the external periphery thereof; the projections 112 bfitted into the depression 111 a upon insertion of the lens 111 into thelens-holding member 112 and serving as engagements are integrally formedwith the lens-holding member 112; and a plurality of the projections 112b are irradiated with the laser light 114, whereby the lens 111 and thelens-holding member 112 are fixed to each other by laser welding.Accordingly, since the lens 111 and the lens-holding member 112 arefixed to each other by laser welding, having the depression 111 ainterposed therebetween, these components are fixed at a so-calledundercut after the laser welding, whereby the lens unit has excellentfixing features of preventing the lens 111 from detaching from thelens-holding member 112 against a detaching force and hence firmlyfixing the lens 111 to the lens-holding member 112.

One skilled in the art will appreciate that the foregoing lens 111 maybe composed of a glass or resin material. In the case where the lens iscomposed of a resin material, upon irradiation with laser light, themelted projections 112 b cause a part of the plastic lens to be melted,and the lens 111 and the lens-holding member 112 are thus laser-weldedwith each other, having the depression 111 a of the lens 111 interposedtherebetween as described above, thereby providing an excellent fixingfeature of preventing the lens from detaching from the lens-holdingmember against a detaching force in the same fashion as described above.

While the lens 111 has the depression 111 a formed at the externalperiphery thereof, and the lens-holding member 112 has the projections112 b formed thereon, fitted into the depression 111 a and serving asengagements in the seventh embodiment, the present invention is notlimited to this arrangement. Even when the lens 111 has depressionsformed at the external periphery thereof, and the lens-holding member112 has a depression formed therein for the depressions to be fittedthereinto, the same advantages can be achieved.

Although no description has been made about the surface of thedepression 111 a of the lens 111, the lens may be formed so as to have arough surface. With this structure, when the lens 111 is composed of aglass material by way of example, the foregoing intermediate memberfills in irregularities of the rough surface, whereby the lens 111 ismore closely fixed to the lens-holding member 112.

Further, while the lens 111 is subjected to laser welding in a state ofbeing simply inserted in the lens-holding member 112 in the seventhembodiment, one skilled in the art will appreciate that the lens unitmay have a structure in which eccentricity and inclination of the lens111 are adjusted in a state of holding the lens 111, for example, by avacuum-sucking tool, and, after the adjustment, the lens 111 issubjected to laser welding while the holding state is maintained. Onthis occasion, since the laser irradiation causes the projections 112 bto expand thermally, the projections 112 b of the lens-holding member112 and the depression 111 a at the external periphery of the lens 111are laser-welded with each other, thereby providing an excellent fixingfeature of preventing the lens from detaching from the lens-holdingmember against a detaching force in the same fashion as in theabove-described sixth embodiment.

Although a lens and lens-holding member included in a pickup opticalsystem are used in the sixth and seventh embodiments, the presentinvention is not limited to the fixing methods using these componentsand is applicable to, an example method in which a filter serving as anoptical member or a neutral density (ND) filter serving as a member foradjusting an amount of light is fixed to a holding member. Further,those skilled in the art will appreciate that the present invention isapplicable to any type of fixing method even when the fixing method isdifferent from the foregoing embodiments or those of fixing theabove-described optical members as long as it meets the spirit of theinvention.

Eighth Embodiment

FIG. 19 is a perspective sectional view of a major part of an opticalunit according to an eighth embodiment of the present invention. Theoptical unit includes a lens 201 serving as one of optical membersforming an image of pickup light from a subject onto a pickup element(lying out of the figure); a lens-holding member 202 for holding thelens 201; and a ring-shaped member 203 serving as an intermediate memberinterposed between the lens 201 and the lens-holding member 202 uponinsertion of the lens into the lens-holding member. The ring-shapedmember is composed of a material shielding visible light and serves alsoas an optical diaphragm shielding light other than the pickup light andharmful light reflected from mechanical components around thering-shaped member and those lying out of the figure. In addition, thering-shaped member has a thermoplastic property and also a propertyabsorbing near infrared light.

The lens-holding member 202 has abutment projections 202 a, againstwhich a bearing-surface 201 a of the lens 201 is abutted upon insertionof the lens into the lens-holding member, formed at three locationsthereof (one of them is not shown) in the circumferential direction atan almost equal interval and defining the position of the lens in theoptical direction. The ring-shaped member 203 has three runoffs 203 aformed at three locations thereof (one of them is not shown) so as tocorrespond to, but not to interfere with the above-mentioned projections202 a. The ring-shaped member is set so as to have a thickness slightlysmaller than the projecting amount of the projections 202 a. With thissetting, when the lens 201 is inserted into the lens-holding member 202,in a state of the bearing-surface 201 of the lens 201 being abuttedagainst the projections 202 a, the ring-shaped member 203 is insertedinto the lens-holding member 202 while the lens 201 and the lens-holdingmember 202 have a slight gap therebetween.

FIG. 20 is a sectional view of a major part of the optical unit in astate in which the lens 201 and the ring-shaped member 203 are insertedin the lens-holding member 202. When a laser irradiation apparatus 204emits near infrared light, as will be described later, the ring-shapedmember 203 is melted such that the lens 201 is fixed to the lens-holdingmember 202.

In accordance with the lens fixing method according to the presentembodiment, the lens 201 and the lens-holding member 202 are fixed toeach other by laser welding in the following order.

In a state in which, the lens 201 is inserted in the lens-holding member202, having the ring-shaped member 203 interposed therebetween asdescribed above, spot-shaped laser light 205 emitted from thelaser-irradiation apparatus 204 passes through the lens 201 first, andthree locations of the ring-shaped member 203 other than the threerunoffs 203 a, more particularly, three locations shown by referencenumber 203 b in FIG. 19 (one of them is not shown), lying on thecircumference and being out of about half-phase with the three runoffs203 a, are irradiated with the laser light 205 substantially at the sametime. Because of being composed of a material absorbent to near infraredlight as described above, upon absorbing the spot-shaped laser light,the ring-shaped member 203 generates heat and is melted. On thisoccasion, the melted ring-shaped member 203 thermally expands so as tofill in the above-mentioned gap between the lens 201 and thelens-holding member 202, whereby the melted ring-shaped member 203 isclosely fixed to the bearing-surface 201 of the lens 201 and also causesthe lens-holding member 202 to be melted so that these two componentsare welded with each other. The process of laser irradiation iscompleted at this stage.

When the laser irradiation is finished and cooling of the irradiatedcomponents starts, although the welding portions of the ring-shapedmember 203 and the lens-holding member contract due to the cooling,since the welding portions of the ring-shaped member 203, thelens-holding member 202, and the lens 201 are integrated into one unitby the welding; hence, the welding portions cannot contract by a volumecorresponding to the above-mentioned gap. As a result, a force isgenerated due the contraction in a direction (A direction indicated inFIG. 20) in which the bearing-surface 201 of the lens 201 is pressedagainst the abutment projections 202 a of the lens-holding member 202,and, after the laser welding, remains so as to press the bearing-surface201 of the lens 201 and the abutment projections 202 a of thelens-holding member 202 to each other, thereby accurately fixing thelens 201 to the lens-holding member 202.

In the above-described embodiment, while the lens 201 and thelens-holding member 202 are laser-welded with each other, having thering-shaped member 203 interposed therebetween, such that there remainsa force generated due to contraction actions, caused by cooling, of thewelding portions of the ring-shaped member 203 and the lens-holdingmember 202, pressing the bearing-surface 201 of the lens 201 against theabutment projections 202 a of the lens-holding member 202, another forcemoving the lens 201 in the radial direction is not generated. Hence,those skilled in the art will appreciate that the lens 201 can besubjected to adjustments such as a so-called eccentric adjustment forguarantee of its optical performance.

Also, while laser irradiation is applied to three locations in theabove-described embodiment, the irradiation locations are not limited tothe above arrangement, and locations of irradiation and the number oflocations can be arbitrarily set as long as these locations lie indisagreement with the runoffs 203 a formed at at least three locationsof the ring-shaped member 203.

Those skilled in the art will appreciate that the foregoing lenscomposed of a glass or resin material is not contrary to the spirit ofthe present invention. In the case where the lens is composed of a resinmaterial, upon laser irradiation, the melted intermediate member causesa part of the resin lens to be melted, whereby the lens and thelens-holding member are laser-welded with each other, having theintermediate member therebetween.

Although no description has been made about the surface of thebearing-surface 201 a of the lens 201, the bearing-surface 201 a may beformed so as to be rough. With this structure, when the lens 201 iscomposed of a glass material by way of example, the foregoingintermediate member fills in irregularities of the rough surface,whereby the lens 201 is more closely fixed to the lens-holding member202.

Ninth Embodiment

FIG. 21 is a perspective sectional view of a major part of an opticalunit according to a ninth embodiment of the present invention. Theoptical unit includes a lens 206 serving as one of optical membersforming an image of pickup light from a subject onto a pickup elementlying out of the figure; a lens-holding member 207 for holding the lens;and a ring-shaped member 208 having a substantially round cross-portionand serving as an intermediate member, which is inserted into a gapproduced upon insertion of the lens, between a slope 206 b formed at thebottom of the external periphery of the lens 206 and a lens-abutmentsurface 207 a of the lens-holding member 207. In the present embodiment,the ring-shaped member 208 has a thermoplastic property and also aproperty absorbing near infrared light.

FIG. 22 is a sectional view of a major part of the optical unit,illustrating its state in which the lens 206 and the ring-shaped member208 are inserted in the lens-holding member 207. As shown in the figure,the ring-shaped member 208 is inserted in the gap produced between theslope 206 b formed at the bottom of the external periphery of the lens206 and the lens-abutment surface 207 a of the lens-holding member 207.On this occasion, the ring-shaped member 208 has a slight gap relativeto the slope 206 b and the abutment surface 207 a. When alaser-irradiation apparatus 209 shown in the figure emits near infraredlight, as will be described later, the ring-shaped member 208 is melted,thereby fixing the lens to the lens-holding member.

In accordance with the lens fixing method according to the presentembodiment, the lens 206 and the lens-holding member 207 are fixed toeach other by laser welding in the following order in substantially thesame fashion as in the first embodiment.

As shown in FIG. 22, in a state in which the lens 206 and thering-shaped member 208 are inserted in the lens-holding member 207,spot-shaped laser light 210 emitted from the laser-irradiation apparatus209 passes through the lens 206 first, and a plurality of locations,more particularly, for example, at least three locations shown byreference numeral 208 a in FIG. 21 (one of them is not shown) of thering-shaped member 208, lying in the circumferential direction at analmost equal interval are irradiated with the laser light substantiallyat the same time.

Because of being composed of a material absorbent to near infrared lightas described above, upon absorbing the spot-shaped laser light, thering-shaped member 208 subjected to laser irradiation generates heat andis melted. On this occasion, the melted ring-shaped member 208 expandsthermally so as to fill in the gap between the slope 206 b formed at thebottom of the external periphery of the lens 206 and the lens-abutmentsurface 207 a of the lens-holding member 207, is closely fixed to theslope 206 b at the bottom of the external periphery of the lens and alsocauses the lens-holding member 207 to be melted. The process of laserirradiation is complete at this stage.

When the laser irradiation is finished and cooling of the irradiatedcomponents starts, although the welding portions of the ring-shapedmember 208 and the lens-holding member contract due to the cooling,since the welding portions of the ring-shaped member 208, thelens-holding member 207, and the lens 206 are integrated into one unitby the welding, the welding portions cannot contract by a volumecorresponding to the above-mentioned gap. As a result, a force isgenerated due to the contraction in a direction (B direction indicatedin FIG. 22) in which a bearing-surface 206 a of the lens 206 is pressedagainst the abutment projections 207 a of the lens-holding member 207,and the force of pressing the bearing-surface 206 a of the lens 206 andthe abutment surface 207 a of the lens-holding member 207 to each otherremains after the laser welding, thereby accurately fixing the lens 206to the lens-holding member 207.

In the eighth and ninth embodiments, while the lens 206 and thelens-holding member 207 are laser-welded, having the ring-shaped member208 interposed therebetween, such that there remains a force generateddue to contraction actions, caused by cooling, of the welding portionsof the ring-shaped member 208 and the lens-holding member 207, pressingthe bearing-surface 206 a of the lens 206 against the abutment surface207 a of the lens-holding member 207, another force moving the lens 206in the radial direction is not generated. Hence, those skilled in theart will appreciate that the lens 206 can be subjected to adjustmentssuch as a so-called eccentric adjustment for guarantee of its opticalperformance.

Further, those skilled in the art will appreciate that even when thelens 206 described in the eighth and ninth embodiments is composed of aglass or resin material, the lens is not contrary to the spirit of thepresent invention. In the case where the lens is composed of a resinmaterial, upon laser irradiation, the melted intermediate member causesa part of the resin lens to be melted, whereby the lens and thelens-holding member are laser-welded with each other, having theintermediate member therebetween.

Although no description has been made about the surface of the slope 206b formed at the bottom of the external periphery of the lens 206, thelens 206 b may be formed so as to rough. With this structure, when thelens 206 is composed of a glass material by way of example, theforegoing intermediate member fills in irregularities of the roughsurface, whereby the lens 206 is more closely fixed to the lens-holdingmember.

While laser irradiation is applied to the three locations in the eighthand ninth embodiments, irradiation locations are not limited to theabove arrangement.

Also, although a lens and a lens-holding member included in a pickupoptical system are used in the eighth and ninth embodiments, the presentinvention is not limited to the fixing methods using these componentsand is applicable to, for example, a method in which a filter serving asan optical member or a neutral density (ND) filter serving as a memberfor adjusting an amount of light is fixed to a holding member. Further,those skilled in the art will appreciate that the present invention isapplicable to any type of fixing method even when the fixing method isdifferent from the foregoing two embodiments or those of fixing theabove-described optical members as long as it falls in the spirit of theinvention.

Further, with respect to the fixing method for fixing, for example, apickup lens and a holding member for holding the pickup lens to eachother by laser welding, according to each of the eighth and ninthembodiments, the lens and the holing member are laser-welded in a statein which these components have an intermediate member interposedtherebetween, having a thermoplastic property. On this occasion, theintermediate member is arranged so as to not lie on a plane defining thepositions of the lens and the holding member in the optical axisdirection, and is also set so as to have a slight gap upon insertion.With this structure, upon laser-welding, the intermediate member expandsthermally so as to fill in the gap, and is welded with the lens-holdingmember, and then with the lens. Although welding portions of theintermediate member and the lens-holding member contract caused bycooling after the welding, since the intermediate member, thelens-holding member, and the lens are integrated into one unit, thesecomponents cannot contract by a volume corresponding to the foregoinggap. As a result, a stress remains in the lens so as to press the lensagainst the holding member, thereby achieving an accurate and reliablelens unit.

With this arrangement, heat generated due to laser welding does notaffect the abutment surface between the optical member and the holdingmember after the laser welding, thereby accurately fixing the opticalmember.

Also, the intermediate member inserted between the optical member andthe holding member is arranged so as to have a gap between thesecomponents upon insertion and is composed of a thermoplastic materialabsorbent to near infrared light, thereby accurately fixing the opticalmember.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed embodiments. On the contrary, the invention isintended to cover various modifications and equivalent arrangementsincluded within the spirit and scope of the appended claims. The scopeof the following claims is to be accorded the broadest interpretation soas to encompass all such modifications and equivalent structures andfunctions.

This application claims priority from Japanese Patent Applications No.2004-132602 filed Apr. 28, 2004, No. 2004-132601, filed Apr. 28, 2004,and No. 2004-163922 filed Jun. 2, 2004, which are hereby incorporated byreference herein.

1. A method for fixing an optical member to a holding member, comprisingthe steps of: inserting the optical member in the holding member havinga plurality of contact portions and a plurality of laser irradiationportions, wherein the inserting step includes inserting the opticalmember in the holding member such that the optical member contacts theplurality of contact portions but does not contact the plurality oflaser irradiation portions; and irradiating the holding member with aplurality of beams of laser light substantially at the same time suchthat the beams of laser light pass through the optical member toirradiate the plurality of laser irradiation portions but not irradiatethe plurality of contact portions.
 2. The method for fixing the opticalmember according to claim 1, wherein the plurality of contact portionsprotrudes more than the plurality of laser irradiation portions, andwherein the irradiating step includes melting the plurality of laserirradiation portions with the beams of laser light so as to contact withthe optical member.
 3. The method for fixing the optical memberaccording to claim 1, wherein the plurality of contact portionsprotrudes more than the plurality of laser irradiation portions,wherein, upon insertion of the optical member in the holding member inthe inserting step, a clearance is defined between the plurality oflaser irradiation portions and the optical member, and wherein theirradiation step includes melting the plurality of laser irradiationportions with the beams of laser light to make the clearance smaller. 4.The method for fixing the optical member according to claim 1, whereineach of the plurality of laser irradiation portions includes a partiallyprotruding portion, wherein, upon insertion of the optical member in theholding member in the inserting step, the partially protruding portioncontacts the optical member, and wherein the irradiating step includesmelting the partially protruding portion with the beams of laser lightto contact with the optical member.
 5. The method for fixing the opticalmember according to claim 1, wherein the plurality of laser irradiationportions has a thickness-reduced portion at a rear surface thereof suchthat the laser irradiation portions have greater elasticity than theplurality of contact portions.
 6. The method for fixing the opticalmember according to claim 1, wherein the plurality of laser irradiationportions has cuts formed therearound such that the laser irradiationportions have greater elasticity than the plurality of contact portions.7. A holding member holding an optical member and fixed by a laserirradiation process, the holding member comprising: a plurality ofpositioning portions adapted to contact with the optical member so as toposition the optical member prior to the laser irradiation process; anda plurality of laser irradiation portions being irradiated with laserlight in the laser irradiation process, wherein the laser irradiationportions do not contact with the optical member prior to the laserirradiation process, wherein the positioning portions and the laserirradiation portions are positioned opposing a single plane of theoptical member, wherein prior to the irradiation process, thepositioning portions protrude more than the laser irradiation portionssuch that the laser irradiation portions do not contact with the opticalmember, and wherein, in the laser irradiation process, the laserirradiation portions melt and come into contact with the optical member.8. The holding member according to claim 7, wherein each laserirradiation portion includes a projection protruding lower than thepositioning portion such that the projection does not contact with theoptical member prior to the laser irradiation process.
 9. The holdingmember according to claim 7, wherein the laser irradiation portions arethinner than the positioning portions.
 10. The holding member accordingto claim 7, wherein each laser irradiation portion includes athickness-reduced portion at a rear surface thereof.
 11. The holdingmember according to claim 7, wherein each laser irradiation portionincludes a cut defined therearound.
 12. An optical unit, comprising: anoptical member having a groove defined around an external peripherythereof; a holding member holding the optical member and having a wallformed therein so as to face the external periphery of the opticalmember; and an intermediate member disposed between the externalperiphery of the optical member and the wall of the holding member, theintermediate member having an elastic ring shape adapted to fit into thegroove, the intermediate member including a thermoplastic resinabsorbent to laser light such that at least a part of the intermediatemember is melted upon irradiation with laser light passing through theoptical member so as to fix the optical member to the holding member.